1. Field of the Invention
The present invention relates to a method of fabricating a piezoelectric vibrating piece, a piezoelectric vibrating piece fabricated by the fabricating method, a wafer used for fabricating the piezoelectric vibrating piece, a piezoelectric vibrator having the piezoelectric vibrating piece, an oscillator, an electronic apparatus and a radiowave timepiece having the piezoelectric vibrator.
2. Description of the Related Art
In recent years, a portable telephone or a portable information terminal apparatus uses a piezoelectric vibrator utilizing quartz or the like as a time source, a timing source of a control signal or the like or a reference signal source or the like. As a piezoelectric vibrator of this kind, various ones are known, and, for example, a piezoelectric vibrator having a piezoelectric vibrating piece of a tuning fork type, a piezoelectric vibrator having a piezoelectric vibrating piece of carrying out a thickness slipping vibration and the like are known.
Explaining by taking an example of a piezoelectric vibrating piece of a tuning fork type, as shown by FIG. 20 and FIG. 21, a piezoelectric vibrating piece 201 includes a piezoelectric plate 212 having a pair of vibrating arm portion 210 arranged in parallel and a base portion 211 integrally fixing base end sides of the pair of vibrating arm portions 210, a pair of exciting electrodes 213 formed at outer surfaces of the pair of vibrating arm portions 210 for vibrating the pair of vibrating arm portions 210, and mount electrodes 214 respectively electrically connected to the pair of exciting electrodes 213. According to the piezoelectric vibrating piece 201, the pair of vibrating arm portions 210 are vibrated in directions of being proximate to or remote from each other when a predetermined drive voltage is applied to the pair of exciting electrodes 213 by way of the pair of mount electrodes 214. Further, at this occasion, a weight of a weight metal film 215 coated at a front end of the vibrating arm portion 210 is previously adjusted (frequency adjustment) to vibrate the pair of vibrating arm portions 210 by a predetermined frequency.
It is general to fabricate a plurality of the piezoelectric vibrating pieces 201 of this kind at a time utilizing a wafer made of various piezoelectric materials of quartz, lithium tantalate, lithium niobate or the like (for example, JP-A-7-212161).
Specifically, as shown by FIG. 22, a raw stone of a piezoelectric material is cut to constitute a wafer S, thereafter, the wafer S is polished to a predetermined thickness. Further, after cleaning, drying the polished wafer S, an outer shape of the piezoelectric plate 212 is formed by etching by a photolithography technology, and a predetermined metal film is patterned to thereby form the respective electrodes and the weight metal film 215. Thereafter, by cutting the respective piezoelectric plates 212 from the wafer S to fragment, a plurality of the piezoelectric vibrating pieces 201 can be fabricated at a time from the single wafer S.
Meanwhile, in a procedure of the fabrication, normally, a frequency adjustment (rough adjustment) of the piezoelectric plate 212 is carried out before fragmentation. Specifically explaining, first, the pair of vibrating arm portions 210 are oscillated by applying a drive voltage by contacting terminals of a frequency adjustor (for example, oscillating circuit, network analyzer or the like) respectively to the pair of mount electrodes 214. Further, the weight of the weight metal film 215 is adjusted by a trimming apparatus (for example, laser or the like) of the frequency adjustor while measuring a frequency at that occasion by the frequency adjustor. Thereby, the frequency adjustment can be carried out.
However, in the method of fabricating the piezoelectric vibrating piece, the following problem remains.
First, in order to carry out a frequency adjustment of the piezoelectric plate, it is necessary to contact the terminals of the frequency adjustor to both of the pair of mount electrodes. That is, it is necessary to contact the two terminals to the one piezoelectric plate. However, the pair of mount electrodes are formed in a state of being aligned in parallel on the outer surface of the piezoelectric plate of a size of a width of about several hundreds μm. Therefore, in order to accurately carry out the contact, it is necessary to position the terminals of the pair of mount electrodes after making the two terminals as proximate thereto as possible. Therefore, a control of the terminal is difficult and the control is obliged to carry out with care. Therefore, time is taken in the frequency adjustment and an efficient operation cannot be carried out.
Further, in recent years, the size of the piezoelectric vibrating piece is downsized, and also an interval between the pair of mount electrodes is narrowed.
Further, in order to carry out the frequency adjustment as efficiently as possible, in the background art, there is also carried out a method of simultaneously contacting two terminals to a plurality of piezoelectric plates to carry out frequency measurement simultaneously by the plurality of piezoelectric plates without adjusting the piezoelectric plates one by one. For example, there is provided a method of dividing a plurality of piezoelectric plates connected to the wafer by a unit of a row, and carrying out frequency measurement of the respective rows. Although thereby, an operational efficiency can be increased, on the contrary, it is necessary to increase a number of terminals of a frequency adjustor twice as much as a number of piezoelectric plates simultaneously vibrated. Therefore, it is necessary to prepare a number of terminals beforehand and it is difficult to achieve a reduction in cost. Further, the control of the terminal is difficult even in accurately contacting the two terminals to the one piezoelectric plate as described above. In contrast thereto, when the frequency adjustment is simultaneously carried out, it is necessary to simultaneously and accurately contact a number of terminals to mount electrodes of a plurality of piezoelectric plates, and therefore, a further difficult operation is constituted.
In addition thereto, when small-sized formation of the size of the piezoelectric vibrating piece is aimed at as described above, the interval between the piezoelectric plates contiguous to each other is further narrowed. Therefore, there is brought about a situation in which the contact of respective twos of terminals to a plurality of piezoelectric plates per se is severe.
Further, as the terminals of the frequency adjustor increases, a number of steps consumed for maintenance of the terminals is needed. Therefore, although the frequency adjusting operation can efficiently be carried out by simultaneously carrying out the frequency measurement of the plurality of piezoelectric plates, on the contrary, a deterioration in maintenance performance is brought about.